Download Skeletal Systems

Skeletal Systems
General Properties of Skeletons
• Connective tissues important in support
– Collagen/tropocollagen molecules
• Molecular rope
• Pack closely together due to glycine content
• Not elastic so good for support
Endoskeletons and Exoskeletons
• Composite materials made of fibers embedded in mineral salts
or organic polymers
– Ex Bone
• Skeletons must withstand forces
–
–
–
–
–
–
Compression
Tension
Shear
Torsion
Stiffness
strength
Endoskeletons and Exoskeletons
• Cost benefit anaylsis
–
–
–
–
–
Exoskeletons
Stiffer but not as strong
Provide excellent support for muscle based movement
Increase in strength requires increase in weight
Animal must molt to grow – skeleton limits space for growth
(predation hazard)
Endoskeletons and Exoskeletons
• Cost benefit anaylsis
– Endokeletons
–
–
–
–
No limit on space for growth ( no molting necessary)
Allows larger body size
Soft tissues prevent skeletal damage
Excellent protection for internal organs
• (heart/lungs)
Hydrostatic Skeletons
• Hydrostatic support from body fluid between cells
• Hydrostatic -of or relating to fluids at rest or to the pressures
they exert or transmit
• Water is incompressible and transmits force in all directions
– apply force to the fluid and it will be transferred to the body wall
– Like a soft hose stiffening when filled with water
Hydrostatic Skeletons
• A hydrostatic skeleton manipulated by muscles can
cause hydraulic movement
– Ex. Squeeze a balloon at one end
– Cnidarians (hydrazoa and anthozoa) rely on hydrostatic
support and hydraulic movement
– Bivalve molluscs use hydraulic mechinism to extent foot.
Hydrostatic Skeletons
• Longitudinal and Circular muscles create peristalsis as
the exert pressure on the hydrostatic skeleton
• See animation
• Good for burrowing or crawling
– Circular wave push front end forward
– Longitudinal contractions broaden the worm making it push
against the burrow
Hydrostatic Skeletons
• Advantages
– Add little weight to the animal
– Little energy needed to carry them around
• Disadvantages
– Precise, local movements difficult
– Contraction in one region stretches muscles in another region
– Punctures of body immobilize the animal
• Cnidarians
Hydrostatic Skeletons
– Hydra – fluids in the gastrovascular cavity act as a skeleton
– 3 layers epidermis – mesoglea – gastrodermis. Collagen
fibers pass spirally around the body
• Perisarc- a delicate exoskeleton secreted by some cnidarians
(chitinous)
• Anthozoans – corals secrete an exoskeleton of calcium
carbonate
Hydra Cell Types
Platyhelmintheyes
• Connective tissue and interstitial fluid are the main
support
• Remember acoelomates!
• Body covered by one cell layer of fiberous basal lamina
• Cestoda and Trematoda have synctial epidermus called
a tegument (absorption)
– Provides body support, resists digestion.
Triploblastic Body Design
based on Hickman Fig. 14-3
Nematoda
• One cell thick outer layer that secretes multilayered
cuticle
• Spiral layers of collagen fibers
• High pressure up to 120 mm Hg
• Provides strong hydroskeletal support
Annelida
•
•
•
•
Flexible cuticle secreted by epidermis
Circular and longitudinal muscles in the cell wall
Septa divide the animal into metameres
Septa allow different pressures in different
metameres
• Creates ability to have more extensive movements
Animals with Exoskeletons
• Arthropoda
– Have a rigid jointed exoskeleton
– Trichogen cells produce setae
Cuticle
• mainly chitin
– Layers
• Endocuticle, exocuticle, epicuticle
–
–
–
–
–
Hardness determined by sclerites (plates of cuticle)
tough, flexible, glucose-amine polymer
stiffened with calcium carbonate in crustaceans
permeable but resists chemicals
waterproofed with waxes in insects
• protection, support, muscle attachment
Exoskeleton Structure
Molting
• Controlled hormonally (ecdysone hormone)
–
–
–
–
–
–
Epidermis secretes molting fluid
Epidermis secretes new cuticle (procuticle)
Molting fluid dissolve the old cuticle
Animal swallows air or water and enlarges, splitting the old cuticle
New cuticle is hardened with sclerites
Animation http://www.aloha.net/~smgon/sutures.htm
Mollusca
• External, rigid, calcerous shell in most for protection of
the soft body.
• Shell produced by mantle
– 3 layers
• Outer = perisostracum (conchiolin)
• Middle= prismatic layer
• Inner = nacerous layer ( alternating layers of calcium and
proteoglycan layers)
Animals with Endoskeletons
• Porifera
– Body of 2 layers
•
•
•
•
Pinacocyte layer on outside and lining cavities
Choanocyte layer on inside
Gelatinous mesohyl in between
Ameobocytes secrete spongin (spongocytes) and spicules
(sclerocytes)
Porifera
Echinodermata
•
•
•
•
Integument of thin ciliated epidermis
Underlying connective tissue dermis
Dermis produces ossicles
Ossicles made from Mg and Ca carbonate crystals bound
together by collagen
• Sea Urchins (asteroidea) Test (shell) made of platelike ossicles
to create a hemispherical endoskeleton
• Spines ( in sockets and movable) project from the ossicles
Chordata
• Endoskeletal notochord
• semi-rigid rod extending the length of the body
• Made from large fluid filled cells encased in concentric
sheathes of connective tissue
• Rigidity from hydrostatic pressure in the cells
Chordata
• Notochord replaced by vertebral column
• Vertebral skeleton
– 2 parts
• Axial skeleton (skull, vertebral column, ribs)
• Appendicular skeleton supports girdles (pectoral and pelvic)
–
–
–
–
–
Articulated skeleton (contains joints)
Sutures (immovable joints)
Bones held together at movable joints by tendons and ligaments
Ends of bones coated with aticular cartilage to reduce wear
Joints lubricated with synovial fluid
• Appendages
Chordata
– Structure reflects mode of locomotion
– Convergence
• Bat (hand) vs Bird wing
Chordata
689-691
• Functions of the Vertebral Skeleton
– Supporting the load of the body
– Amphibian skeletons project laterally and bear less weight whereas bird and mammal
skeletons are positioned under the body and bear more of a load
– Arched for supporting the weight of visceral below it. ( like a suspension bridge)
– Load Bearing
• Muscles and skeleton work together
• Bones bear shear and torsion, muscles bear load
– Ex jumping on femur bone and bowing
– Protection
– Mineral storage
Chordata
188
• Functions of the Vertebral Skeleton
– Protection
•
•
•
•
Operculum protects gills
Skull protects brain and inner ear
Sockets protect eyes
Ribs protect heart and lungs
Chordata
188
• Functions of the Vertebral Skeleton
– Mineral Storage
• Calcium and Phosphorous reservoir
• Calcium – parathormone and calcitonin
Chordata
• Vertebrate Skeletal Materials
– Cartilage
• Connective tissue formed by chodrocytes
– Matrix of collagen fibers and proteoglycans joined by hyaluronic acid, with
chondroitin sulfate and keratan sulfate
Chordata
•
Vertebrate Skeletal Materials ( 190)
– Bone
• Long bone
–
–
Hollow tube (diaphysis) with expanded hollow end (epiphysis)
Bone marrow in cavity
• Outer surface = periosteum
–
attachment of tendons and ligaments
• Compact vs spongy bone
• Nutrient canals, osteons, haversian systems
• Lacunae, osteocytes, canaliculi
Chordata
– Vertebrates have skeleton of fibrous connective tissue
cartilage or bone
– Bone formation
• Endochondral bone formation
– (1) Fibrous connective tissue
– (2) cartilage
– (3) osteocytes and bone matrix
• Dermal (membrane) bone
– (1) fibrous connective tissue
– (2) bone
Chordata
– Visceral and Somatic components
• Gill arches
– Formerly filter feeding structures